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Urbanite #49 July 08
By: Greg Hanscom
We humans are choosy about the company we keep,
particularly when it comes to animals. Dogs and cats
and guppies and gerbils can share our space, but the
rest of the Animal Kingdom belongs Out There, in
Nature.
Nature, however, has a habit of jumping fences, and
when it does, Tom Scollins’ phone rings.
Scollins, a compact 34-year-old who wears
wraparound sunglasses, khaki fatigues, and black,
police-style boots, grew up a stone’s throw from the
Bronx Zoo. As a youngster, he was known to spend
snowy days in the warm reptile house, watching the
frogs and salamanders. (“I was kind of a strange kid,”
he allows.) He went on to become a zookeeper, and
worked in the Baltimore Zoo’s reptile house for a few
years. He now runs TS Wildlife Control, a one-man
business based out of his house in Govans.
When starlings nest in the dryer vent, Scollins gets
the call. When a squirrel slides down the chimney
and ping-pongs around in the basement, he gets the
call. When a black rat snake emerges from the
shadows in the laundry room, the panicked
homeowner calls Scollins—no matter the hour, no
matter the weather—and asks him to come put the
beast back Outside, where it belongs.
Scollins has plucked a couple of wayward raccoons
from the cliff face at the National Aquarium’s stillunder-construction Australia exhibit. He has
descended into the bowels of the downtown post
office to flush a Cooper’s hawk out of the sorting
rooms. He was once summoned to trap a groundhog
that was nibbling the flowers outside a “massage
parlor” on Eastern Avenue. “This woman comes to
the door wearing nothing but a bra and panties,” says
Scollins. “I’m standing there with my clipboard—‘Um,
did you call about a groundhog?’”
Wild animals travel through our alleys and storm
drains. They feed on our scraps, and nest in the
overlooked corners of our attics, yards, and parks. (In
May, a mallard hatched eleven ducklings in a
sidewalk planter on Pratt Street.) They are here in
spite of, and sometimes because of, us, and they
stubbornly refuse to go away.
Tom Scollins understands this in-between world of
urban wildlife by instinct and experience. But
Baltimore has also become a laboratory for a cadre
of researchers who are trying to make sense of the
“urban ecosystem.” These researchers, who hail from
universities across the country, operate under the
federally funded Baltimore Ecosystem Study. They
are breaking scientific ground, and in the process,
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shining some light on our often troubled relationship
with wildlife. Their research suggests that, while
Baltimore’s human residents may always rule over its
wild ones, this town may well be big enough for the
both of us.
Until recently, urban ecology was at best an obscure
sub-discipline in a field focused on more pristine
places. Mary Cadenasso, an ecologist at the
University of California Davis and one of the principal
researchers with the Baltimore Ecosystem Study,
remembers an ecology conference in the mid-1990s.
When a woman asked about her work, Cadenasso
mentioned that she was researching forest patches in
the Bronx. The response: “Well, that’s not ecology.”
Cities, it seems, were just too messy for mainstream
ecologists. The ideal study site was an island of
wildlife habitat unaffected by the world around it. And
in fact, islands were the inspiration for a field of
ecological thinking, which was crystallized in the
1967 book The Theory of Island Biogeography by
ecologist Robert MacArthur and biologist Edward O.
Wilson. Here’s the Cliff’s Notes version: Big islands
closer to the mainland tend to harbor a greater
diversity of wildlife than smaller, more isolated ones.
It makes sense: A small isolated island is hard to get
to, and even if a small population of birds, say,
managed to gain a foothold, inbreeding or the
inevitable tsunami or a hurricane would eventually
wipe them out.
These principles laid the groundwork for how people
thought for decades about protecting wildlife, both on
islands and off. To stave off a growing wave of
extinctions, conservationists have advocated for
creating large wildlife reserves across continents—
the equivalent of large islands in the ocean—and
then connecting them with corridors to allow animals
to migrate and interbreed.
But islands have proven to be imperfect metaphors.
“Island biogeography theory is binary,” says
Cadenasso. “It’s islands versus water, good versus
bad habitat.” Most terrestrial ecosystems resist such
simple divisions, she says, because the “sea”
surrounding most habitat “islands” is often dotted with
shrubs, trees, or other features that can be of use to
wildlife.
Cadenasso and others have championed a new way
of thinking about terrestrial ecosystems—one that
takes into account the complex hodgepodge of
habitat and human development that spatters a
growing share of the landscape. They call the new
approach “patch dynamics,” and it’s a perfect fit for
ecological studies in cities, with their ever-evolving
landscapes of houses and parks, development and
decay.
Steward Pickett, an ecologist at the Cary Institute of
Ecosystem Studies in Millbrook, New York, did the
pioneering work in patch dynamics in the 1970s and
’80s, working in forests in New Jersey and
Pennsylvania. When he moved to New York, he
began to look at forests in a more urban context. (He
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was Cadenasso’s advisor when she was working in
the Bronx.) “The more we studied these [urban]
forests, the more we thought, we ecologists need to
understand people. We need to work with social
scientists, historians, and economists,” he says.
They found those people in Baltimore.
Sometime in 1993 or ’94, Pickett received an e-mail
from Morgan Grove, then a doctoral candidate at the
Yale School of Forestry and Environmental Studies.
Grove had come to Baltimore in 1989 as a master’s
student, and had helped set up a partnership
between Yale, the nonprofit Parks & People
Foundation, and what was then called the Baltimore
City Department of Parks and Recreation: Called the
Urban Resources Initiative, it broke new ground in
natural resource management, and put Baltimore
residents of all ages to work planting trees and
restoring streams. For his dissertation, Grove was
studying neighborhoods in the Gwynns Falls
watershed, to see if class and race had any bearing
on the distribution of vegetation, which slows and
filters stormwater runoff. While his research was
more sociology than ecology, he asked Pickett if the
principles of patch dynamics still applied.
“Steward was really excited. He’d finally met a social
scientist who understood ecology,” says Grove.
Not long thereafter, Pickett and a handful of his
colleagues accepted Grove’s invitation to come to
Baltimore. In addition to the Urban Resources
Initiative, they found an engaged group of local,
state, and federal agencies, and a city with a rich
history and distinct neighborhoods that lent
themselves nicely to the patch dynamics approach. “I
just thought, this is the perfect place to build a new
kind of ecology,” says Pickett.
In 1996, Pickett, Grove, and Parks & People
President Jacqueline Carrera went to the federally
funded National Science Foundation, which was in
the process of setting up a nationwide network of
long-term ecological research sites. The following
year, the foundation selected Baltimore and Phoenix,
Arizona, for six-year research grants (since extended
for another six years), giving urban areas a little
street cred in nature-lovers’ circles, and urban
ecology a significant financial boost.
With Pickett as project director, Grove leading the
social science, and Parks & People building local
partnerships, the Baltimore Ecosystem Study has
pulled together researchers from disciplines ranging
from soil science to forestry and urban design. Much
of the research has focused on broad systems—
stormwater runoff, nitrogen cycling, socioeconomic
factors shaping the urban ecosystem—but it has also
looked at urban wildlife, and the results are intriguing.
I met Chrissa Carlson on the stoop of her Waverly
rowhouse on a sunny May morning, her kinky blond
hair pulled into pigtails. “I have something to show
you,” said the animated 29-year-old. She
disappeared inside for a moment, and returned with a
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small bundle folded into a brown paper bag. She
carefully unwrapped a marshmallow-sized lump of
black, white, gray, and yellow. “It’s a magnolia
warbler,” she said. “I found it in my backyard
yesterday.”
We admired the dead bird, which was likely passing
through when it died, headed north from its wintering
grounds in Central America or the Caribbean. Then
she took it back inside and put it in her freezer for
safekeeping. (When I inquired about the bird a week
later, she told me that it was in a Mason jar,
embalmed in diluted vodka: “I want to display him
with some of my other curiosity-shop-esque objects,
but he is floating at the top of the jar.”)
Next, Carlson grabbed her binoculars, jammed a
worn copy of the National Geographic Field Guide to
the Birds of North America into the back of her
capris, and started down the sidewalk. As she
walked, she pointed out the neighborhood’s feathery
residents, which she recognized by their songs—the
more reliable identification method when working in
the woods, where you’d otherwise have to spot a bird
the size of a fingerling potato flitting about a tangle of
leaves forty feet up. “There’s a robin over there, and
cardinals,” she said. “That’s a mockingbird.” She
pointed toward the source of twittering over our
heads: “Those are chimney swifts—the ones that
look like cigars with wings.”
Carlson was trying to show me that birds, like people,
are picky when it comes to real estate. Her block,
where there were a few ample yards and a scattering
of trees and shrubs, seemed to suit robins,
mockingbirds, and the ubiquitous lipstick-red
cardinals. Just to the south, on a nearly treeless
block of rowhouses, we found only house sparrows
and starlings, both European imports that have made
themselves all-too-comfortable in American cities.
Then we walked west across Greenmount Avenue
and stepped into the shady, tree-lined confines of
Guilford. The air lit up with birdsong. “There’s a
Carolina wren over there,” said Carlson, pointing to a
hedge across the street. We spent a few minutes
ogling a chestnut-sided warbler, then walked on,
Carlson pointing out a red-eyed vireo, a bronzeheaded cowbird, a song sparrow, and a northern
parula. Our final stop was a patch of woods adjacent
to Druid Hill Park, where we watched a veritable
Mardi Gras parade of birdlife, including an orchard
oriole, a cousin of Baltimore’s flamboyant avian icon.
This tour of the town’s bird neighborhoods served as
the background for Carlson’s master’s research with
the Baltimore Ecosystem Study, which she told me
about as we walked. In the spring and summer of
2005, Carlson frequented fifteen forest patches
among the houses along the tributaries of the
Gwynns Falls. Her goal was to learn something about
what made the woods in these neighborhoods
attractive—or not—to birds looking to hunker down
and raise kids.
The work was not always pleasant. She described
bushwhacking through “trashy little snags of woods,
practically in people’s backyards, cursing nature.”
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The poison ivy didn’t bother her too much, she said,
“but multiflora rose and other thornies were the bane
of my existence”—not to mention Lyme disease,
which
she fortunately discovered early enough to avoid any
lasting health issues.
In the end, though, it all paid off. Carlson summed up
her findings thusly: “Birds like trees.”
After months of number crunching, a more nuanced
picture began to emerge from her data. As island
biogeography theory would dictate, the bigger forest
patches harbored a richer array of bird species. But
when she factored in the landscape within a 100meter buffer surrounding the woods, she saw that
there was more to it.
Using a land-use classification system called
HERCULES (short for High Ecological Resolution
Classification of Urban Landscape and
Environmental Systems) developed by Mary
Cadenasso, Carlson broke the buffers into seventytwo different kinds of patches, based on vegetation,
buildings, and surface materials. Her results showed
that forest patches in neighborhoods with lots of
mature trees harbored more species than those in
neighborhoods with fewer trees. In fact, contrary to
popular ecological thinking, the surrounding
neighborhood had a stronger bearing on the birdlife
in forest patches than did the structure of the forest
itself.
A paper based on the study, co-authored by Carlson,
Mary Cadenasso, and Gary Barrett at the University
of Georgia, is being considered for publication in the
journal Landscape and Urban Planning. It was a
single, small study, and Carlson cautions that it is
difficult to draw any hard conclusions. But if her
findings hold up, they have some interesting
implications: What we plant in our yards can have a
substantial impact on the birdlife in neighboring green
spaces. In other words, all the nature-magazine
admonishments about decorating your yard with
wildlife-friendly native plants may be more than just
hype.
Baltimore is peppered with parks—six thousand
acres worth. With a little work from the neighbors,
those parks might be stretched to accommodate a
greater diversity of wild creatures.
All this begs the question: Is it wise to encourage
wildlife to live in cities, where encounters with the
dominant species often end in disaster? One need
look no farther than the sides of our roads to see
what happens when wild animals get too close.
Exploding deer populations, which cause car crashes
and spread Lyme disease, have long bedeviled
Maryland suburbanites.
Tom Scollins, the wildlife control expert, says that the
root cause of most negative encounters with wildlife
is laziness: A contractor doesn’t spend the extra few
bucks to screen off a bathroom vent, creating an
attractive nest hole; a motorist tosses food out the
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window, attracting scavengers to the roadside; a
restaurant leaves its dumpster open, creating a
ready-made feast. With a little more care, he says,
we can learn to live together more peaceably. “We’re
never going to exclude wildlife from urban areas,” he
says. “We just have to learn to coexist.”
Chrissa Carlson and others are quick to point out that
cities will never be havens for whole, healthy wild
animal communities. Where humans reign,
“generalist species” that can make use of a variety of
habitat and food often thrive—think raccoons and
starlings. But there are plenty of other, more
specialized creatures that will never hunker down in a
little forest patch in the city. There are songbirds that
would fall prey to our fluffy, subsidized predators—
and then there are nature’s large predators, like
bears and wolves, that need more room than even an
animal-friendly city can provide; only large nature
reserves will work for them.
But if Baltimore can make itself more wildlife- and
ecosystem-friendly, it will provide a valuable lesson
for the world, says Steward Pickett. Eighty percent of
Americans live in cities, and this year, the world
population as a whole will pass the halfway mark:
According to the United Nations, for the first time in
history, more people will live in cities than out. In
China, Latin America, and Africa, cities are rising
almost overnight.
“The bad news is that in much of the world, this
urbanization is badly planned,” says Pickett. “A lot of
the people moving into cities are living in
shantytowns and horrible slums. Twenty-first century
urbanism is showing some of the horrors of 19th
century urbanism.”
Unless we learn to better integrate cities into the
natural world, we’re bound to repeat the mistakes of
the past—on a much larger scale, says Pickett. We
leave cities out of our ecological equations at our
own, and the planet’s, peril.
And cities do harbor more than just raccoons, rat
snakes, and starlings.
Baltimore, for its part, is a waypoint on the aerial
superhighway traveled by millions of migrating birds
each spring and fall—birds, like Chrissa Carlson’s
magnolia warbler, that winter in the tropics, but breed
up north. During migration in Patterson Park, “it can
sound like you’re in the middle of Canada
someplace,” says ecologist David Curson, director of
bird conservation for the National Audubon Society’s
Maryland-D.C. office. “The trees come alive with the
sounds of rose-breasted grosbeaks, blackpoll
warblers, and Swainson’s thrushes.”
There’s another bird that makes a surprising showing
here—and not just for a refueling stop. The least tern,
a robin-sized seabird with knife blades for wings, flies
all the way from the Caribbean to nest around
Baltimore. Curson, a soft-spoken 44-year-old who got
his start watching birds as a kid in London, is
charged with keeping an eye on them.
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Curson and I load into his persnickety Toyota Matrix
one early June morning and head east from his office
across the street from the Patterson Perk coffee
shop. Just outside the Beltway, we stop at a low,
brick building emblazoned with the words “Patapsco
Patriots Achieve With Integrity.” This is Patapsco
High School, and the birds we’re looking for
immediately show themselves, rising above the
rooftop with a din of piercing cries.
Beneath us, the building echoes with the voices of
nine hundred high school kids. Around us are
rowhouses, and over the rooftops to the south, we
can see the former Bethlehem Steel plant and the
Sparrows Point Shipyard. But here, on this gritty
rooftop island, there is a nesting colony of a rare and
sensitive species. We count seventy birds in all, fortyfour of them sitting with their breasts pressed down
against the gravel, tails cocked up. Curson says
these birds are likely incubating tiny, speckled eggs,
though I can’t pick them out amid the rocks. I do spot
a fuzzy, gray chick, however, that emerges from
beneath one of the birds to gobble up a small fish
delivered by another parent from a nearby creek.
From time to time, the colony sends up a squadron of
birds that circles and dives—an effective defense
against crows or hawks. But up here, they don’t have
to worry about cats or raccoons—or people, with the
exception of an occasional maintenance worker or
Curson, who is careful to disturb them as little as
possible.
There are those who would use the tern’s feat of
adaptive re-use to argue that wild animals are
capable of adjusting to a human-dominated world—
that they should be left to evolve or die. But the least
terns on the Atlantic coast, I discover, are the
exception to the rule. The country’s two other least
tern populations—one that nests on the California
coast, the other along the Mississippi River—sit on
the brink of extinction. And there are many other
examples of species that are blinking out as we carve
across the landscape.
Still, the tern’s story suggests that an urban world
does not have to be an ecologically impoverished
one. By choice or by accident, we create niches,
patches, and opportunities for wild creatures. They’ll
be with us as long as we’re around, doing their thing
as we do ours—and with a little thought, we can
make their lives easier, and our lives richer.
Curson and I visit three schools and two warehouses
over the course of the day, and each time, we are
greeted with skepticism. Told of the birds, one janitor
jokes, “Are they good to eat?” A woman working the
desk at a warehouse says sure, she’s seen the birds:
“They’ve been pooping all over our cars.” Curson
politely answers questions, hands out literature, and
tells the story of the indomitable bird on the rooftop.
His enthusiasm is infectious. One employee,
intrigued by Curson’s tale, asks, “Where are the birds
from?”
“Well,” Curson says thoughtfully, “they’re from here.”
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—Greg Hanscom is Urbanite’s senior editor. He has
a 10-year-old Chesapeake Bay retriever named
Finnegan.
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